Transmit-receive switch



Feb 18- l947- N. E. LlNDl-:NBLAD TRANSMIT-RECEIVE swITcH Filed Sept. 30, 1945 2 Sheets-Sheet l QMS NM@ Ok Omi INVENT'OR E. L/lndenlad )fww ATroRNEY Nm. Om,

Fell 18, l947 N. E. LINDENBLAD TRANSMIT-RCEIVE SWITCH Filed sept. 50, 1945 2 Sheets-sheet 2 ,nantcirCuit ',atfathird point.` Y. the transmitter' to the' antenna is energized,l thereiisjn'o currentl at Patented Feb. 18, 1947 AUNITED STATE 2,416,105,` franNsMir-asosrvn swrrcn Nils E. Lindenblad, Rocky Point, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application september so, 1943., serial No. 504,373

The present-J invention relates to high frequency filter systems for connecting together one or more transmitters and receivers to a common antenna system and, mo-re particularly, to such systems for use in pulse transmitting and receiving systems used in radio detecting and ranging.

An object of the present invention is the provision of a filter device -for the selective coupling of a transmitter Aand receiver toa common antennasystemjwithout requiring the use of mechanical switches.

.Another object of the present invention is the provision of a lter network, Athe operating characteristics of which are controlled by power applied thereto.

Still another object of the present invention is the provision of an antenna and iilter device for pulse transmitting and receiving equipment which utilizes no moving parts cr mechanical switches for diverting outgoing and incoming impulses to the appropriate directivity equipment.

Still another object of the present invention is the provision of a circuit which may be used inv a self-synchronized vsystem for effecting the switching of transmitter and receiver line connec'tions to an antenna.

A further'obiect of the `present invention is the provision of a circuit, as aforesaid, in which thev ineii'ectiveness of the switch during certain portions of its operating cycle is eliminated.

Still a further object of the present invention is the provision otv a circuit, as aforesaid, which operates efciently vover a considerable band of frequencies.

The .foregoing objects and others, which may appear from the following detailed description,

Aare attained 'in accordance with the principles of the present invention by coupling the trans- 23 Claims. (Cl. 'Z50-413) mission line from the'transmitt'er to the antenna to a resonant circuit twice at a spacing of one wavelength between the coupling points. The coupling is in opposing phase relationship at the two coupling points so that when the lineis energized, the resonant circuit is inactive. Two

spark gaps are provided in series with the line in the loop between the two coupling points to the resonant circuit. rlhe iirst spark gap is at a distance of a half wavelfrcm the couplingpont of the line coming from the transmitter. The next gap is a quarter wave from the other lpoint of coupling of the transmission y line to the reso- I nant circuit.V A r-eceiver is coupled to thelresoj- No'w when the line 'from the point where it is coupled to the resonant circuit since this point is located a half wave from the first gap. When the first gap breaks down, the secondgap also breaks down. As the two gaps break down, there is a cancellation in the resonant circuit from the keffect of the equal and oppositely l,applied current through the Atwo,

points. The resonant circuit, therefore, remains inactive and, the receiver is, therefore, entirely uncoupled` from the transmission line.

When a received signal comes from the antenna,"the distance between the lirst gap and the yresonant circuit is aquarter wavelength. A current maximum develops at this point of coupling and the resonant circuit becomes energized. This energization cannot, however, aiieot the coupling of the transmitter since this line is opened by the second gap at a distance of a half wave vfrom the coupling point, thereby introe ducing a very high series line impedance at the coupling point. None of vthe received power is applied to the transmitter and all of the received power is vcoupled to the receiver. The couplings tothe resonant circuit'may be very close so that in the receiving condition the resonant circuit is highly loaded and circulating currents are kept low. This also increases the effective band width vof frequencies over which the device operates over that permissible in previous systems, of which I am aware.

The present vinvention will be Amore ful-ly understood hy reference to thejfollowing detailed description, which is accompanied by drawings, in which:

Figure 1 illustrates diagrammatically an ap-A plication'oi` the invention to a` complete radio direction and ranging system;

Figure 2 illustrates in cross-sectional view. an.

embodiment ofthe invention; and

Figure 3 illustrates .a modification .ofV the fornil of the invention shownjin Figure 2. Referring, now, to Figure 1, there Jis Vshown'a 'radio vdetection and ranging system'including a 'directional antenna |50 'having mounted atthe tennaQduring' eachgquadrantal position of the The timing of the energization of the c eiver I6 apply received reflected signal impulses the The structural details and manner of operation of the charge reverser and transmitter are Ymore fully disclosed in my prior application United States SerialrNo. 441,311, filed May l, 1942 (RCA 1).#20978), to which reference may be made for a more detailed disclosure.

The antenna I2 is arranged to be selectively l coupled to transmitter I8 and receiver 22 through a transmitter-receiver switch, indicated generali ly as reference numeral 24. This transmitter-receiver switch, Vin accordance Y, with the present inventionsincludes an entirely enclosed drumlike chamber 26 having its interior dimensions so chosen as to be space-resonant to the operating frequency of the system.A A concentric cable transmission line from receiver 22 is coupled to l the resonant cavity 26 by having its inner conductor 29 pass through'the space withincavity 26 -from one end wall to the other and connect to the far wall of the cavity. There `is likewise `a vcoaxial cable transmission line 30 connected from the Ytransmitter to the antenna I2. The in- [ner conductor 3| of this transmission line passes through the resonant cavity 26 at points 32 and 34 and is thus coupled to the cavity twice in opposingrelationships. v mission Vline 30 between coupling points 32 and `34.is chosen as one wavelength. Thus circuits `passing through the line are in phase at'the two couplingpoints 32 and 34, and since they pass throughthe cavity in opposite directions, the net "couplingis zero. lan operating wavelength from point 32 in con- `ductor 3I is a series gap 35`with a second series lgap 36-located at a distance equal to one quarter The distance along trans- At a distance equal to `half of of the operating wavelength from point .34 in conductor 3|.

the couplings at 29, 32 and 34 of equal magnitude `thus avoiding any transformation from the intercoupled cavity 26. The degree of the couplings to cavityfZt` may be very high so that inthe receiving condition thecavity is so loaded downV that circulating currents are kept low. This also increases the effective band width of frequencies overwhich theV device operates. Y ,v Now inthe operation of the system shown in lFigure 1, as motor I4 operates to switch the directivity '.of the antenna around the axis of the applied'by'means of transmission line 30 to the antenna I2. Since gap 35 is ata distance o f 'onehalf wavelength from coupling pontr32as long to other deflecting and control circuits in indi- 3, cator 20, whereby the direction and range of reflecting object may be determined.

L VIf transmission lines 28and 3 0have'the same Qcharacteristic impedance` it lis desirable to make end walls 5i and 52 of each of the apertures.

as gap 35 is open, there is no coupling between up thereacross, gap 36 simultaneously breaks down and the energy flows to the antenna I2. Since conductor 3i passes through cavity 26 at points 32 and 34 in opposite direction and the points 32 and 34 are one wavelength apart, there isa cancellation of energy coupled to the cavity and the cavity remains inactive. Therefore, no energy is applied from the transmitter I5 to the receiver I6. Y Y

- With the cessation of the impulse from transmitter I5, gaps 36 and 35 cease to be'conductive, and the system is then ready to receive an incoming impulse reflected from a distant object. When the reflected impulse is received in the antenna I2, it is conducted along conductor 3I to point 34 where conductor 3l is coupled to resonant chamber 26. Since point 34 is spaced from lgap 36 by a distance equal to aquarterof the op- ;erating wavelength and 36 is open, conductor 3l is effectively grounded at point 34. Therefore, conductor 3'I is coupled to the resonant chamber 26 in the same Way as conductor 29 of transmission line 36 is coupled to chamber 26. Therefore, the received impulse is picked up by transmission line '28 conveyed to receiver I6. Since point 32 of the transmission line 36 is one-half wavelength from the open circuit at gap 35, there is a high impedance at point 32, and no coupling exists between the cavity 25 and conductor 3I of transmission line 30 where it emerges to go to transmitter I8. Therefore,v none of the received power is applied to the transmitter.

The received impulse applied to receiver 22 is rectified and applied to indicator 20 to operate, for example, the vertical deflection circuits of a cathode ray tube, the horizontal deflection circuits being controlled by pulses from the charge reverser i6. From the indications on the cathode ray tubes contained in indicator2ll, the range and direction of the object from which the received impulse was reflected can be determined in a manner well known in the art and which will, therefore, not be further described at this time.

Figure 2 of the drawings shows in greater detail a preferred form of construction of the transmitter-receiver switch 24 of Figure l. Here it will be seen that the resonantcavity 26 may `be constructed in the form of a short cylinder havingend plates 5I and 52 and a cylindrical side Wall 53. For the purpose of tuning chamber 26to the desired operating frequency, end wall 52 carries a threaded plug 54 which may be screwed into or out of the chamber 2E to change its. operating frequency. The transmission line 28from the receiver has its outer shell connected to end wall 5i, while the inner conductor 29 passes through the chamber 26 and is conductively connected to theend wall 52. End walls 5I and 52 alsoyeach contain a pair of aligned apertures through'which conductor 3i of transmission line 3G passes. The outer shell of transmission line 3l) is ccnductively connected to the In order to maintain the conductor 3| in rigid alignment where it passes through cavity 26, short,n

r circuited quarter wave stubs 55 and r 56 are provided at one passage point, while stubs 57 yand Y '58 vare Vprovided at the other passage. Each stu-b is connected in-shunt between the inner conductor 3I and the outer shell of the transmission line.

These stubs might as far as their supporting function is concerned, be substituted vby insulating rings, if desired. However, shorted-quarterwave stubs result in lower losses than would the insulating rings. In addition, stubs 56 and El carry through the inner conductor portions thereof threaded rods di! and 6I by means of which the spacing of spark gaps 35 and 36 may be adjusted from the exterior by Vmeans of knobs G2 and 151i. The quarter-wave portion of inner conductor 3i" between gaps 3,5 land 35 is supported in position by another shunt-connected shorted--duarizerewave stub f65.

The modification of the present invention shown in Figure 3 is particularly useful for longer wavelength systems, where the resonant chamber 26 of Figures l and 2 would be unduly large. Therefore, the functions of the resonant chamber 25 in this figure are taken over by a `resonemt circuit 55 including an outer shell 6'! closed at the ends by end plates E8 and GS and an inner central conductor 'i9 .having an electrical length equal to one quarter of the operating wavelength. Central conductor 'lil is con nected at one end to end plate 59, while the other end is unconnected. If desired, 'the actual physical length of central conductor 'lll .may be somewhat less than one quarter of the operating wavelength, and it may carry at its free end a capacitive loading member such that its electrical length is equal to a quarter wavelength at the operating frequency.

In this modification, concentric transmission line i3d from the transmitter has its inner conductor itl' passed through outer shell Sl radially inwardly through the space between the shell i5? and the inner conductor lil, and out through end wall 6s, Thus transmission line '30 forms a one wavelength loop and again passes up through end wall 69 to the interior of inner conductor l0. rihere the inner conductor I3! again passes radially outwardly through to the outer shell B1. From there vtransmission line |35 is connected to the antenna, not shown. The transmission line 128 from the receiver has its inne-r conductor lili! passed radially through the outer shell 6l and conductively connected to the `inner conductor le. The transmission line l53| contains in the looped portion a pair of series gaps 35 and 535. Gap |35 is spaced onehalf of the operating wavelength from the point where the transmission line from the transmitter passes through the central conductor lil, and gap E35 is spaced one quarter of the operating wavelength from the point where the transmission line again passes through the central conductor lil. The operation of this modification of the invention is exactly'the same as that heretofore described.

While I have illustrated a particular embodiment of the present invention, it should be clearly understood that it is not limited thereto since many modications may be made in the several elements employed and in their arrangement and it is, therefore, contemplated by Athe appended claims to cover any such modifications as fall within the spirit and scope of the invention.

I claim:

l. A switching device including a resonant circuit, a transmission line adapted to be connected between a transmitter and an antenna, meansffor coupling said transmission line to said circuit at j two points yalong the length of said line spaced .apart a distance substantially'equal to one operating. wavelength, said couplings being in opposingpha-se relationships, -a receiver coupled yto said resonant circuit, and means serially connected `in saidtransmission line between said points of cou- .plingfor selectively controlling the continuity of said line.

' Y2. A switching device including a resonant circuit, a 'transmission line Vadapted to be connected betweenqan Yintermittently operative transmitter and an antenna, means for coupling lsaid Acircuit to said transmission line at two points, said couplings being in electrically opposing relationships, a receiver coupled to said resonant circuit, and means associated with said transmission line for causing both of said couplings to be effective during operating periods of said transmitter and for causingonly the coupling associated with said antenna to be effective between such periods.

3. A switching device including a resonant circuit, a `transmission line adapted to be connected between an intermittently operative transmitter and an antenna, means for coupling said circuit to said transmission line at two points, said couplings being in opposingphase relationships, a receiver `coupled to said resonant circuit, resonant elements associated with each of said coupling means, said resonant elements causing said couplings to be ineffective during operating periods of said transmitter, and means associated with said transmission line for causing both of said couplings to be effective during operating periods of said transmitter and for causing only the coupling associated with said antenna to be effective between such periods.

4. A switching device including a resonant chamber, a transmission line adapted to be connected between a transmitter and an antenna,

means for coupling said transmission line to said chamber at two points along the length of said line spaced apart a distance equal to a multiple including unitary of one operating Wavelength, said couplings being in opposing phase relationships, a receiver also coupled to said resonant chamber, and means serially connected in said transmission .line between said points of coupling for selectively controlling the continuity of said line.

5. A switching device including a resonant circuit, a transmission line adapted to be connected between a rst transducer and a second transducer, means for coupling said transmission line to said circuit at two points along the length of said line spaced apart a distance substantially equal to one operating wave-length, said couplings being in opposing relationships, a third transducer coupled to said resonant circuit, and means serially connected in said transmission line between said points of coupling forselectively controlling the continuity of said line.

6. A switching device including a resonant circuit, a transmission line adapted to be connected between an intermittently operative first transducer and a second transducer, means for coupling said circuit to said transmission line at two points, said couplings being in opposing phase relationships, a third transducer coupled to said res- Y onant circuit, and means associated with said transmission line for causing both of said couplings to be eifective during operating periods of said first transducer and for causing only the coupling associated with said second transducer to be. effective between such periods.

rl. A switching device including a resonant circuit, 'a ltransmission. line adapted to be connected between a transmitter and an antenna, means for vcoupling `said transmission line to saidcircuitat two poi-nts along the llength of said line spaced aparta distance equal to one operating wavelength, said couplingsV being in opposing relationships, alreceiver coupled to said resonant circuit, and means serially connected in said transmission line between said points of coupling for selectively controlling the continuity of said line,said means being so arranged that when said line is discontinuous between said points said antenna is coupled to said circuit. l i Y8. A switching device including aresonant circuit, a transmission line adapted to be connected between a transmitter and an antenna, means for coupling said transmission line to said circuit at two points along the length of said line spaced apart a distance equal to one operating wavelength, said couplings being in opposing relationships, a receiver coupled to said resonant circuit, and means seriallyYA connected in said transmission line between said points of coupling for selectively controlling the continuity of said line, said means being so arranged that when said line is discontinuous between said points said antenna is coupled to said circuit and said transmitter is uncoupled from said circuit.

9. A switching device including a resonant chamber, a transmission line adapted to be connected between a transmitter and an antenna, said transmission line passing through said rescnant chamber at two points spaced along the length of said line a distance equal to one operating wavelength, said passes through said resonant chamber being in opposite directions, a secondtransmission line coupled to `said resonant chamber, said nrst transmission line having a pair of series gaps therein between said two passes through said resonant chamber, one of said gaps being oneV quarter of the operating wavelength from one pass and the other gap being spaced one half ofthe operating wavelength from the other pass.

10. A switching device including a resonant circuit, a transmission line adapted to be connected between a transmitter and an antenna, said transmission line being coupled to said resonant circuit at two points spaced along the length of said line a distance equal to one operatingV wavelength, said couplings being in opposite senses, a second transmission line coupled to saidresonant circuit, said first transmission length from the other of said couplings.

l1. A switching device including a resonant circuit, a transmission line adapted to be connected between a transmitter and an antenna, said transmission line being coupled to said resonant circuit at two points spaced along the length ci said line a distance equal to one operating wavelength, said couplings being in opposite senses, a second transmission line coupled to said resonant circuit, said iirst transmission line having a pair of series gaps therein between said two points of coupling to said resonant circuit, one of said gaps being one quarter of the operatingwavelength from thel one of said couplings adjacent said antenna and the other gap being spaced one half of the operating wavelength from the other of said couplings, said resonant circuit including a conductive outer shell surrounding a` 8 quarter wave inner conductor, said innerv conductor being connected to said shell at one end.

12. A switching device including a resonant circuit, a transmission line adapted to be connectedbetween a transmitter and an antenna, said transmission line being coupled to said resonant circuit at two points spaced along the length of said line a distance substantially equal to one operating wavelength, said couplings being in opposite senses, a second transmission line coupled to said resonant circuit,said first transmission line having a pair of series gaps therein between said two points of `coupling to said resonant circuit, one of said gaps being one quarter of the operating wavelength from the one of said couplings adjacent said antennav and the other gap being spaced one half of the o-perating wavelength from the other of said couplings, said resonant circuit including a conductive outer shell surrounding a quarter wave inner conductor, said inner conductor being connected to said shell at one end, said transmission line passing radiallir between said outer shell and inner conductor near said one end.

13. A switching device including a resonant chamber, a transmission. line adapted to be connected between a transmitter and an antenna, said transmission line having a conductor passing through said resonant chamber at two points spaced along the length of said line a distance substantially equal to one operating wavelength, said passes through said resonant chamber being in opposite directions, Va second transmission line coupled to said resonantcharnber, said rst transmission line having a pair of series gaps in said conductor between said two passes through saidV resonant chamber, one of said gaps being one quarter of the operating wavelength from one pass and the other gap being spaced one half of the operating wavelength from the other pass.

14. A switching device including a resonant chamber, a concentric transmission line having an outer shell and an inner conductor and adapted to be connected between a transmitter and an antenna, the inner conductor of said transmission line passing through said resonant chamber at two points spaced along the length of said line a distance substantially equal to one operating wavelength, said passes through said resonant chamber being in opposite directions, a second'transmission line coupled to said resonant chamber, said rst transmission line having a pair of series gaps in its inner conductor between said two passes thro-ugh said resonant chamber, one of said gaps being one quarter of the operating wavelength from one pass and the other gap being spaced one half of the operating wavelength from the other pass, said inner conductor being supported in concentric relationship with the outer shell at each side of eachpassage through said chamber by shuntconnected short-circuited quarter wave stubs, each also including an outer shell andan inner conduct-or.

l5. A switching device including a resonant chamber, a concentric transmission line having an outer shell and an inner conductor and adapted to be connected between a transmitter and an antenna, the inner conductor of said transmission line passing through said resonant chamber, said flrst transmission line having a pair of series gaps in its inner conductor between said two passes through said resonant chamber,

one of said gaps being oneA quarter of the operating wavelength from one pass .and the other gap being spaced one half of the operating wavelength from the other pass, said inner conductor being supported in concentric relationship with the outer shell at each side of each passage through said chamber by shunt-connected shortcircuited quarter wave stubs, each also including an outer shell and an inner conductor, and means for adjusting the length of said series gaps passing through the inner conductor of adjacent quarter Wave stubs.

16. A switching device including a resonant chamber, a concentric transmission line having an outer shell and an inner conductor and adapted to be connected between a transmitter and an antenna, the inner conductor of said transmission line passing through said resonant chamber at two points spaced along the length of said line a distance substantially equal to one operating wavelength, said passes through said resonant chamber being in opposite directions, a second transmission line coupled to said resonant chamber, said first transmission line having a pair of series gaps in its inner conductor between said two passes through said resonant chamber, one of said gaps being one quarter of the operating wavelength from one pass and the other gap being spaced one half of the operating wavelength from the other pass, said'inner conductor 'being supported in concentric relationship with the other shell at each side of each passage through said chamber by shunt-connected short-circuited quarter wave stubs, each also including an outer shell and an inner conductor, means for adjusting the length of said series gaps passing through the inner conductor of adjacent quarter wave stubs, and means for varying the resonant frequency of said chamber including a conductive plug screwed into an end wall of said chamber.

17. A high frequency circuit including a resonant device, a transmission line adapted to be connected between a transmitter and an antenna, means for coupling said transmission line to said resonant device at two points along the length of said line, said couplings being such as to normally tend to cancel one another, a receiver coupled to said resonant device, and means so arranged in said transmission line between said lpoints of coupling as to selectively control the continuity of said line whereby only the coupling i more closely adjacent said transmitter may be disabled.

18. A switching device including a resonant circuit, a transmission line adapted to be connected between an intermittently operative transmitter and an antenna, means for coupling said resonant circuit to said transmission line at two points, said couplings being such as to normally tend to cancel or neutralize one another, a receiver coupled to said resonant circuit, and means associated with said transmission line for effecting both of said couplings during operating periods of said transmitter and for disabling only the coupling more closely adjacent said transmitter between such periods.

19. A switching device including a. resonanty chamber, a transmission line adapted to 'be connected between a transmitter and an antenna,

means for coupling said transmission line to said chamber at two points along the length of said line, said coupling means being so arranged that said couplings normally tend to substantially neutralize one another, a receiver coupled to said resonant chamber, and means serially connected in said transmission line between said points of coupling for selectively controlling the continuity of said line, said last-mentioned means being so located that when the continuity Of said line is brokenuonly said coupling more closely adjacent saidltransmitter is disabled.

20. A high frequency circuit including a transmitter, a receiver, and an antenna, atransmission vline coupling said transmitter to said an.V

tenna, a resonant device coupled to said receiver, and two couplings between said resonant device and said transmission line, said couplings being in such relationship as to normally tend to neutralize one another.

21. A high frequency circuit including a trans'- mitter, a receiver, and an antenna, a transmission line coupling said transmitter to said antenna, a resonant device coupled to said receiver, and twocouplings between said resonant device and said transmission line, said couplings being in such relationship as to normally tend to neutralizeone another, and means associated with said transmission line for disabling one of said couplings.

22. A high frequency circuit including a trans- .mitter, a receiver, and an antenna, a transmission line coupling said transmitter to said antenna, a resonant device' coupled to said receiver and two couplings between said .resonant device and said line, said couplings being so arranged as to normally tend to neutralize one another, said transmission line having a portion forming a common path between said receiver and said antenna and said transmitter and said antenna.

23. A high frequency circuit including a transmitter, a receiver, and an antenna, a transmission line coupling said transmitter to Said antenna, a resonant device coupled to said receiver and two couplings between said resonant device and said line, said couplings being so arranged as to normally tend to neutralize one another, said transmission line having a portion forming a common path between said receiver `and said antenna and said transmitter and said REFERENCES CITED The following references are of record in the nie of this patent:

UNITED STATES PATENTS Name Date Number Alford Feb. 21, 1939 

